New portable wireless communications systems have recently increased the demand of electronics circuits, such as RF-amplifiers, mixers and local oscillators related to various transmitters and receivers. Typically, they are implemented in form of integrated circuits. An important field are low noise amplifiers LNA. Prior art integrated circuits within the RF range are e.g. disclosed in:
1! Robert G. Meyer, "A 1-GHz BiCMOS RF Front-End IC", IEEE Journal of Solid State Circuits, Vol. 29, No. 3, March 1994, p. 350-355.
2! Asad A. Abidi, "Low-Power Radio-Frequency IC's for Portable Communications, Proceedings of the IEEE, Vol. 83, No. 4, April 1995, p. 544-569.
Recently, various kinds of two-stage circuit configurations have been introduced for low noise amplifiers LNA. Very frequently, topologies consisting of a cascade connection of a common-emitter amplifier stage and another stage are preferred. In most cases, cascade connections are based on the gain developed by the common-emitter stage. On the other hand, it is well known that the common-emitter connection suffers heavily from the Miller effect. The Miller effect is often reduced by loading the common-emitter stage with a low input impedance of a common base circuit used as a second stage of the cascade. In practice, this reduces the overall gain a great deal. In brief, such configurations suffer from the difficulty in matching up the high internal input and output impedances of the different stages of the cascade.